Distances to high-velocity clouds

AST-0607152研究：密歇根州立大学PI：Timothy BeersTITLE：到高速云的距离ABSTRACTDR密歇根州立大学的Timothy Beers将与其合作者Bastiaan Wakker博士(威斯康星大学麦迪逊分校)、Donald York博士(芝加哥大学)和Ronald Wilhelm博士(德克萨斯理工大学)共同开展一个项目，以确定到14个所谓的高速云(HDC)和中速云(IVCs)的距离。这些是巨大的中性氢气云，它们以与简单的星系自转模型不相容的速度移动。这一目标将通过首先从中分辨率光谱确定视线上到蓝色水平分支(BHB)恒星的距离，然后从高分辨率光谱中从星云中寻找星际吸收特征来实现。通过确定哪些光谱揭示了云的特征，并知道了光谱所来自的恒星的距离，就可以获得对到云的距离的限制。到这些云的距离仍然是银河系天文学中的突出问题之一，解决这些云的性质将为星系形成和演化的模型提供重要的约束，这项工作将对天文学的各个子领域，特别是星系的形成和演化产生广泛的影响。该计划的组成部分是独立的，非常适合研究生和本科生的研究项目。还将开展外联活动。

AST-0607152INSTITUTION: Michigan State UniversityPI: Timothy BeersTITLE: Distances to High-Velocity CloudsABSTRACTDr. Timothy Beers (Michigan State University), along with collaborators Dr. Bastiaan Wakker (University of Wisconsin at Madison), Dr. Donald York (University of Chicago) and Dr. Ronald Wilhelm (Texas Tech University), will undertake a program to determine the distances to 14 so-called high-velocity clouds (HVCs), and intermediate-velocity clouds" (IVCs). These are massive clouds of neutral hydrogen gas that are moving with velocities that are incompatible with simple models of galactic rotation. The goal will be accomplished by first determining the distances to blue horizontal branch" (BHB) stars along the line of sight from medium-resolution spectra, and then looking for interstellar absorption features from the clouds in high-resolution spectra. By determining which spectra reveal the signature of the clouds, and knowing the distances to the stars from which the spectra were derived, constraints on distances to the clouds can be obtained. Distances to these clouds remain one of the outstanding problems in Galactic astronomy, and resolution of the nature of these clouds will provide important constraints on models of galaxy formation and evolution.The work will have broad impact on various sub-fields of astronomy, particularly galaxy formation and evolution. Components of the program are self-contained, and well-suited for graduate and undergraduate research projects. Outreach activities will also be undertaken.